feat: Add missing port number to surl when creating request via API

Fix: requests failing due to missing port numbers. https://sdc-dev.astron.nl/stageit/requests/35923/

• Also add missing port numbers in LTARequestSerializer, instead of only in draft requests.
• Move the add_srm_port_number_if_missing method to new surl_utils file to prevent circular import error.
• Also fix missing port numbers when restarting a (failed) requests